Apparatus and method for manufacturing a cable bolt

ABSTRACT

An apparatus for manufacturing a cable bolt includes a rotatably driven pay-out reel ( 20 ) for paying out a cable ( 1 ) coiled in use about the pay-out reel ( 20 ). An upstream accumulator ( 40 ) is located downstream of the pay-out reel ( 20 ) for accumulating cable ( 1 ) advanced from the pay-out reel ( 20 ). A bulb forming device ( 80 ) is located downstream of the upstream accumulator ( 40 ), for forming a bulb ( 2 ) in cable ( 1 ) advanced from the upstream accumulator ( 40 ). A cable drive ( 60 ) is located downstream of the upstream accumulator ( 40 ), for advancing cable ( 1 ) through the bulb forming device ( 80 ). The pay-out reel ( 20 ) is configured to rotate at least substantially continuously whilst the cable drive ( 60 ) is configured to advance the cable ( 1 ) after formation of each bulb ( 2 ) to a position for formation of a subsequent bulb ( 2 ) in the cable. The cable drive ( 60 ) stops a central portion ( 1   b ) of the cable downstream of the upstream accumulator ( 40 ) for formation of the subsequent bulb ( 2 ), the upstream accumulator accumulating or decumulating an upstream portion ( 1   a ) of the cable ( 1 ) as required throughout operation of the apparatus to allow at least substantially continuous rotation of the pay-out reel ( 20 ) whilst the central portion ( 1   b ) of the cable ( 1 ) is stationary.

TECHNICAL FIELD

The present invention relates to the field of strata control, and in particular relates to an apparatus and method for manufacturing a cable bolt form of rock bolt for securing the roof or wall of a mine, tunnel or other ground excavation.

BACKGROUND OF THE INVENTION

Rock bolts are utilised to secure the roof or walls of an underground mine, tunnel or other ground excavation by inserting the rock bolt into a bore hole drilled in the face of the rock to be secured and securing the rock bolt within the hole. One known form of rock bolt is a cable bolt (sometimes called a strand bolt) that includes a plurality of wires helically wound into the form of a cable.

In one known cable bolt installation method, grout (or resin) is injected into the bore hole after insertion of the cable bolt so as to encapsulate at least part of the length of the cable, securing the cable bolt within the bore hole once the grout has set. A rock face plate is typically attached to the exposed end of the cable bolt and arranged to bear against the rock face to thereby apply a compressive load against the rock face, stabilizing the same. In order to increase the bond strength between the cable bolt and the grout encapsulating the cable bolt, it is known to form one or more bulbs in the cable bolt, thereby locally increasing the cross sectional area of the cable bolt, acting to resist pulling of the cable bolt through the grout.

In previously proposed techniques of forming bulbs along the length of a cable bolt, a pair of longitudinally spaced clamps are arranged to releasably clamp a cable, with one of the clamps being longitudinally displaceable in relation to the fixed clamp by way of an hydraulic ram. In operation, the cable is clamped with the two clamps in a spaced apart relationship, with the displaceable clamp then being displaced toward the fixed clamp, thereby buckling the wires of the cable between the clamps, resulting in the formation of a bulb in the cable bolt.

Various arrangements have been proposed for advancing the cable to form successive bulbous portions spaced along the length of a cable. In the simplest form, a length of cable is manually advanced after forming each successive bulb. This manual process is, however, labour intensive and results in particularly slow production rates. Arrangements have also been proposed that utilise the clamps that form the bulbs, either alone or in combination with additional clamps and hydraulic rams, to advance the cable after forming each successive bulbs. Again, however, such arrangements provide for relatively slow production rates. Also previously proposed is an arrangement that provides for a semi-continuous production of bulbed cable bolts, supplying coiled cable from a pay-out reel to a bulb forming device with the resulting cable being taken up by a rotatably driven take-up reel. To allow the formation of each successive bulb, both the pay-out reel and the take-up reel must be temporarily stopped whilst the clamps of the bulb forming device are activated to clamp the cable and form the bulb. Following formation of the bulb and release of the clamps, the pay-out reel and take-up reel must be brought back up to speed from a stationary state. Continually stopping and starting the pay-out and take-up reels limits production rates and is relatively inefficient, requiring the use of excess energy to stop and start the reels in each bulbing sequence.

There are also difficulties associated with the various methods of controlling advance of the cable to ensure successive bulbs are accurately spaced.

OBJECT OF THE INVENTION

It is the object of the present invention to substantially overcome or at least ameliorate at least one of the above disadvantages.

SUMMARY OF THE INVENTION

In a first aspect, the present invention provides an apparatus for manufacturing a cable bolt, said apparatus comprising:

a rotatably driven pay-out reel for paying out a cable coiled in use about said pay-out reel;

an upstream accumulator, located downstream of said pay-out reel, for accumulating cable advanced from said pay-out reel;

a bulb forming device, located downstream of said upstream accumulator, for forming a bulb in cable advanced from said upstream accumulator;

a cable drive, located downstream of said upstream accumulator, for advancing cable through said bulb forming device;

wherein said pay-out reel is configured to rotate at least substantially continuously whilst said cable drive is configured to advance the cable after formation of each bulb to a position for formation of a subsequent bulb in the cable, said cable drive stopping a central portion of the cable downstream of said upstream accumulator for formation of the subsequent bulb, said upstream accumulator accumulating or decumulating an upstream portion of the cable as required throughout operation of said apparatus to allow at least substantially continuous rotation of said pay-out reel whilst the central portion of the cable is stationary.

Typically, said apparatus further comprises:

a downstream accumulator, located downstream of said bulb forming device and said cable drive, for accumulating cable advanced from said bulb forming device; and

a rotatably driven take-up reel for taking up cable advanced from said downstream accumulator;

wherein said take-up reel is configured to rotate at least substantially continuously, said downstream accumulator accumulating or decumulating a downstream portion of the cable as required throughout operation of said apparatus to allow at least substantially continuous rotation of said take-up reel whilst the central portion of the cable is stationary.

In one form, said cable drive is located upstream of said bulb forming device.

The upstream accumulator may be configured to engage an upstream portion of the cable and deflect the path of the upstream portion of the cable in a direction tending to maintain a constant tension in the upstream portion of the cable.

Typically, said upstream accumulator comprises a pulley mounted on a displaceable shaft.

The downstream accumulator may be configured to engage a downstream portion of the cable and deflect the path of the upstream portion of the cable in a direction tending to maintain a constant tension in the upstream portion of the cable.

Typically, said downstream accumulator comprises a pulley mounted on a displaceable shaft.

Typically, said bulb forming device comprises:

a first clamp adapted to releasably clamp the central portion of the cable with the central portion of the cable extending along a longitudinal axis;

a second clamp longitudinally spaced from said first clamp and adapted to releasably clamp the central portion of the cable with the central portion of the cable extending along said longitudinal axis; and

a clamp displacement drive for longitudinally displacing said first clamp, relative to said second clamp, along said longitudinal axis.

In one form, the apparatus further comprises a cutting device, located downstream of said bulb forming device for cutting cable advanced from said bulb forming device,

wherein said downstream accumulator and said take-up reel are displaceable from an operative position downstream of said bulb forming device.

In a second aspect, the present invention provides an apparatus for manufacturing a cable bolt, said apparatus comprising:

a cable supply;

a bulb forming device, located downstream of said cable supply, for forming a bulb in cable advanced from said cable supply;

a cable drive, located downstream of said cable supply, for advancing cable through said bulb forming device;

a downstream accumulator, located downstream of said bulb forming device and said cable drive, for accumulating cable advanced from said bulb forming device; and

a rotatably driven take-up reel for taking up cable advanced from said downstream accumulator;

wherein said said take-up reel is configured to rotate at least substantially continuously whilst said cable drive is configured to advance the cable after formation of each bulb to a position for formation of a subsequent bulb in the cable, said cable drive stopping a central portion of the cable between said cable supply and said downstream accumulator for formation of the successive bulb, said downstream accumulator accumulating or decumulating a downstream portion of the cable as required throughout operation of said apparatus to allow at least substantially continuous rotation of said take-up reel whilst the central portion of the cable is stationary.

In one form, said cable drive is located upstream of said bulb forming device.

The downstream accumulator may be configured to engage a downstream portion of the cable and deflect the path of the upstream portion of the cable in a direction tending to maintain a constant tension in the upstream portion of the cable.

Typically, said downstream accumulator comprises a pulley mounted on a displaceable shaft.

Typically, said bulb forming device comprises:

a first clamp adapted to releasably clamp the central portion of the cable with the central portion of the cable extending along a longitudinal axis;

a second clamp longitudinally spaced from said first clamp and adapted to releasably clamp the central portion of the cable with the central portion of the cable extending along said longitudinal axis; and

a clamp displacement drive for longitudinally displacing said first clamp, relative to said second clamp, along said longitudinal axis.

In a third aspect, the present invention provides a method for manufacturing a cable bolt, said method comprising:

rotatably driving a pay-out reel having a cable coiled thereon to pay-out said cable from said pay-out reel;

operating a cable drive, located downstream of said pay-out reel, to advance said cable through said cable drive and a bulb forming device;

operating said cable drive to intermittently stop a central portion of said cable whilst continuing to rotatably drive said pay-out reel;

whilst said central portion of said cable is stopped, forming a bulb in said central portion of said cable with said bulb forming device; and

accumulating an upstream portion of said cable, located upstream of said cable drive and said bulb forming device, whilst said central portion of said cable is stopped.

The method typically further comprises the steps of:

rotatably driving a take-up reel, located downstream of said bulb forming device, to take up cable advanced from said bulb forming device; and

accumulating a downstream portion of said cable, located downstream of said cable drive and said bulb forming device, whilst said portion of said cable is being advanced.

In a fourth aspect, the present invention provides a method for manufacturing a cable bolt, said method comprising:

supplying cable from a cable supply;

operating a cable drive, located downstream of said cable supply, to advance said cable through said cable drive and a bulb forming device;

rotatably driving a take-up reel, located downstream of said bulb forming device, to take up cable advanced from said bulb forming device;

operating said cable drive to intermittently stop a central portion of said cable whilst continuing to rotatably drive said take-up reel;

whilst said central portion of said cable is stopped, forming a bulb in said central portion of said cable with said bulb forming device; and

accumulating a downstream portion of said cable, located downstream of said cable drive and said bulb forming device, whilst said portion of said cable is being advanced.

In a fifth aspect, the present invention provides a method for manufacturing a cable bolt, said method comprising:

a) driving a cable along a longitudinally extending path through a bulb forming device having an upstream clamp and a downstream clamp longitudinally spaced from said upstream clamp;

b) at a position upstream of said bulb forming device, measuring displacement of said cable along said path whilst said cable is being driven;

c) stopping at least a portion of said cable extending through said bulb forming device upon a first predetermined measured displacement of said cable equal to said displacement measured at step b);

d) clamping said portion of said cable with said upstream clamp and said downstream clamp;

e) displacing said upstream clamp towards said downstream clamp, thereby longitudinally compressing said portion of said cable to form a bulb in said portion of said cable;

f) unclamping said portion of said cable;

g) further driving said cable along said path;

h) at said position upstream of said bulb forming device, measuring further displacement of said cable along said path whilst said cable is being further driven;

i) stopping at least a further portion of said cable extending through said bulb forming device upon a further predetermined measured displacement of said cable equal to said further displacement measured at step h);

j) clamping said further portion of said cable with said upstream clamp and said downstream clamp;

k) displacing said upstream clamp towards said downstream clamp, thereby longitudinally compressing said further portion of said cable to form a further bulb in said further portion of said cable;

l) unclamping said further portion of said cable; and

m) repeating steps g) to l).

In a preferred form, steps b) and h) are performed with a measuring device, output of said measuring device during steps d) and h) being disregarded when measuring displacement of said cable.

Typically, said measuring device is a rotary shaft encoder.

The shaft encoder may be mounted on a wheel engaging said cable, said shaft encoder measuring rotation of said wheel.

Alternatively, said shaft encoder may be coupled to a drive shaft of said cable drive, said shaft encoder measuring rotation of said drive shaft.

In one form, immediately prior to unclamping said portion of said cable in step f), and immediately prior to unclamping said further portion of said cable in step l), a force applied to said upstream clamp to displace said upstream clamp toward said downstream clamp is removed, thereby allowing said upstream clamp to be displaced away from said downstream clamp during elastic recovery of said portion of said cable and during classic recovery of said further portion of said cable.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will now be described, by way of an example only, with reference to the accompanying drawings wherein:

FIG. 1 is a plan view of an apparatus for manufacturing a cable bolt;

FIG. 2A is a side elevation view of the apparatus of FIG. 1 immediately prior to the formation of a bulb in a cable;

FIG. 2B is a side elevation view of the apparatus of FIG. 1 immediately after formation of a bulb in the cable;

FIG. 3 is a side elevation view of the cable drive of the apparatus of FIG. 1;

FIG. 4A is a side elevation view of the bulb forming device of the apparatus of FIG. 1 during advancement of a cable;

FIG. 4B is a side elevation view of the bulb forming device of FIG. 4A with the first and second clamps thereof clamping the cable in preparation for forming of a bulb; and

FIG. 4C is a side elevation view of the bulb forming device of FIG. 4A during formation of a bulb.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1, 2A and 2B depict an apparatus for manufacturing a cable bolt. The apparatus is in the form of a continuous production line and comprises a pay-out reel 20, an upstream accumulator 40 located downstream of the pay-out reel 20, a cable drive 60 located downstream of the upstream accumulator 40, a bulb forming device 80 located downstream of the upstream accumulator 40 (and typically downstream of the cable drive 60), a downstream accumulator 100 located downstream of the bulb forming device 80 and a take-up reel 120 located downstream of the downstream accumulator 100.

The pay-out reel 20 in use is provided with a supply of cable 1 coiled on the pay-out reel 20. The pay-out reel 20 is rotatably driven about an axle 21 by a drive motor 22 via a conventional reduction gearbox 23, chain 23 a and driven sprocket 24 mounted on the axle 21.

The pay-out reel 20 advances the cable 1 to the upstream accumulator 40. The upstream accumulator 40 is configured to accumulate and decumulate an upstream portion 1 a of the cable 1, as will be discussed further below. In the embodiment depicted, the upstream accumulator 40 is configured to engage the upstream portion 1 a of the cable 1 and is here in the form of a “dancer roll”, being a pulley 41, hereinafter referred to as the upstream dancer roll 41, mounted on a displaceable shaft 42. The shaft 42 is mounted on a block 45 which in turn is slidably mounted in the vertically extending slot 44 of a tower 43. The slot 44 acts as a guide for the block 45. The shaft 42 and upstream dancer roll 41 are thus vertically displaceable, generally transverse to the roughly horizontal path of the upstream portion 1 a of the cable 1. A first idler wheel 46 is located in the path of the cable 1 between the pay-out reel 20 and the upstream dancer roll 41, whilst a second idler wheel 47 is located downstream of the upstream dancer roll 41. The first and second idler wheels 46, 47 serve to isolate the upstream portion 1 a of the cable 1 that is acted on by the upstream accumulator 40. Displacement of the upstream dancer roll 41 in a direction against the upstream portion 1 a of the cable 1, here in a downward direction, deflects the cable, increasing the length of the path of the cable 1 between the first idler wheel 46 and second idler wheel 47, thereby accumulating cable. Displacement of the upstream dancer roll 41 in a direction away from the cable 1, (upwards in the arrangement depicted) reduces deflection, and thereby length, of the path of the cable 1, thereby decumulating cable.

In the arrangement depicted, a pneumatic cylinder 48 is mounted on the top of the tower 43. The block 45 is coupled to a piston 49 located within the pneumatic cylinder 48 by way of a piston rod 50. The pneumatic cylinder 48 is pressurized so as to apply downward pressure on the piston 49 and thereby apply a downward force on the block 45, forcing the upstream dancer roll 41 into engagement with the upstream portion 1 a of the cable 1. The pneumatic pressure within the cylinder 48 acts against the vertical force component of the tension in the upstream portion 1 a of the cable 1 that results from deflection of the upstream portion 1 a of the cable. As the deflection of the upstream portion 1 a of the cable 1 increases, the tension in the upstream portion 1 a of the cable 1 tends to increase and pressure in the cylinder 48 tends to decrease. Conversely, as deflection of the upstream portion 1 a of the cable 1 decreases, the tension in the upstream portion 1 a of the cable 1 tends to decrease and the pressure in the cylinder 48 tends to increase. It is also envisaged that the cylinder 48 may be provided with a regulator, whereby pressure within the cylinder 48 remains constant. It is also envisaged that the pneumatic cylinder 48 might be omitted, with the dancer roll 41 acting under its own weight due to gravity only to engage the upstream portion 1 a of the cable 1.

The cable drive 60 is depicted in further detail in FIG. 3. The cable drive 60 comprises a pair of opposing caterpillar style endless belts 61, 62 that engage the upper and lower extremities respectively of the cable 1. Each of the belts 61, 62 is driven through an endless loop about an upstream idler pulley 63, 64 and downstream driven pulley 65, 66. The driven pulleys 65, 66 are driven by a drive motor 67 via a primary gear box 68, drive shaft 69 and secondary gear boxes 70. As an alternative, it is envisaged that the driven pulleys 65, 66 may each be directly driven by separate motors controlled to remain in phase by way of electronic variable speed drives.

Still referring to FIG. 3, longitudinal displacement of the cable 1 along its longitudinal path is measured by way of a rotary shaft encoder. FIG. 3 depicts two alternative configurations for such a shaft encoder. A rotary shaft encoder is a known electro-mechanical device that translates rotational motion into an electrical signal, typically in the form of pulses, that may be readily converted into a measurement of linear displacement. In a first configuration, a rotary shaft encoder 71A is directly coupled to the drive shaft 69 of the cable drive 60. In a modified form of the first configuration, the drive motor 67 is in the form of a stepper motor that has an integral shaft encoder that is coupled to the drive shaft 69 by way of the drive motor output. In an alternative and preferred configuration, a rotary shaft encoder 71B is coupled to an encoder wheel 72 that engages the cable downstream (or alternatively, immediately upstream) of the cable drive 60. An idler wheel 73 is located directly opposite the encoder wheel 72 to ensure that the encoder wheel 72 remains in contact with the cable 1 and is rotated by the advancing cable 1 without slippage. The rotary shaft encoder 71A, 71B has a fixed housing 74A, 74B and rotating internal encoder shaft 75A, 75B that is fixed to the drive shaft 69 (in the configuration with the encoder 71A) or the encoder wheel 72 (in the configuration with the encoder 71B). Typically, either by electro-optical or electro-magnetic means, a pulse is generated for each rotary displacement of the encoder shaft through a set angle. These pulses can be readily processed into a measurement of displacement of the cable 1 through the known relationship between a single revolution of either the drive shaft 69 or encoder wheel 72 and linear displacement of the cable 1.

An embodiment of the bulb forming device 80 is depicted in greater detail in FIGS. 4A through 4C. The bulb forming device 80 is of the form described in Australian Patent Application No. 2005209572 to the present applicant, the entire contents of which are incorporated herein by cross-reference. The bulb forming device 80 comprises first (upstream) and second (downstream) clamps 81, 82 adapted to releasably clamp the central portion 1 b of the cable 1 extending along a longitudinal axis L defining the path of the central portion 1 b of the cable 1 through the bulb forming device 80. The first clamp 81 comprises serrated upper and lower jaws 83, 84 and a first hydraulic clamping ram 85 attached to the first clamp upper jaw 83 for driving the first clamp upper jaw 83 into engagement with the cable 1, thereby clamping the cable 1 between the first clamp upper and lower jaws 83, 84. The first clamp guides 86 maintain the first clamp upper and lower jaws 83, 84 in alignment. The second clamp 82 is similarly comprised of a second clamp upper jaw 87, second clamp lower jaw 88, a second hydraulic clamping ram 89 and second clamp guides 90.

The first clamp 81 is longitudinally displaceable relative to the second clamp 82 along the longitudinal axis L by way of a clamp displacement drive, here in the form of an hydraulic ram 91. The plunger 91A of the hydraulic ram 91 is attached to the first clamp 81 by way of a cam mechanism 92, described in greater detail in Australian Patent Application No. 2005209572, that rotates the first clamp 81 as it is longitudinally displaced by way of the hydraulic ram 91. Specifically, the cam mechanism 92 comprises a cylinder 93 that is rotationally fixed relative to the first clamp 81 and a cylindrical cam housing 94 that receives the cylinder 93. The cylinder is provided with a cam follower in the form of a radially projecting pin 95 that engages an inclined cam slot 96 provided in the wall of the housing 94. Accordingly, longitudinal displacement of the cylinder 93 relative to the housing 94 results in rotation of the cylinder 93 relative to the housing 94 by virtue of the cam arrangement. The hydraulic ram 91, cam housing 94, and second clamp 82 are each mounted on a fixed base 97. It is envisaged that the bulb forming device might omit the rotating cam mechanism 92 such that the first clamp 81 does not rotate as it is longitudinally displaced. It is also envisaged that the bulb forming device may take any of various other known forms.

Downstream of the bulb forming device 80 is a cutting device 98 that may be utilized to cut the cable 1 into predetermined lengths as desired.

The downstream accumulator 100 is of the same general form as the upstream accumulator 40. The downstream accumulator 100 engages the downstream portion 1 c of the cable and is again in the form of a “dancer roll”, being a pulley 101 mounted on a displaceable shaft 102 and hereinafter referred to as the downstream dancer roll 101. The shaft 102 is mounted on a block 105 which in turn is slidably mounted in the vertical extending slot 104 of a tower 103. The slot 104 acts as a guide for the block 105. A third idler wheel 106 is located in the path of the cable 1 between the cutting device 98 and the downstream dancer roll 101, whilst a fourth idler wheel 107 is located downstream of the downstream dancer roll 101. As with the upstream accumulator 40, the downstream accumulator 100 may be provided with a pneumatic cylinder 108 mounted on top of the tower 103. The block 105 is coupled to a piston 109 located within the pneumatic cylinder 108 by way of a piston rod 110. The pneumatic cylinder 108 operates in the same general manner as described above in relation to the cylinder 48 of the upstream accumulator 40, and may again be pressure regulated if desired. It is again also envisaged that the pneumatic cylinder 108 may be omitted, with the downstream dancer roll 101 acting under gravity only.

The take-up reel 120 is also of the same general form as the pay-out reel 20. The take-up reel 120 advances the cable 1 from the downstream accumulator 100. The take-up reel is rotatably driven about an axle 121 by a drive motor 121 via a reduction gearbox 123, chain 123 a and driven sprocket 124 mounted on the axle 121. Immediately upstream of the pay-out reel 120 is provided a distribution wheel 125 to laterally guide the downstream portion 1 a of the cable 1 across the lateral extent of the take-up reel 120 so as to evenly coil the cable onto the take-up reel 120. In this regard, the distribution wheel 125 is laterally driven along an axle 126.

Operation of the apparatus will now be described. A supply of cable 1 is firstly coiled onto the pay-out reel 20 with its leading end manually fed through the apparatus onto the take-up reel 120 ready for the commencement of continuous cable bolt production. The cable 1 is advanced over the top of the first idler wheel 46, directly beneath the upstream dancer roll 41, over the second idler wheel 47, through the cable drive 60, through the bulb form device 80, over the third idler wheel 106, beneath the downstream dancer roll 101, over the fourth idler wheel 107, over the distribution wheel 125 and onto the take-up reel 120. The entire production line is operated by a control system (not depicted).

Primary control of the various components of the production line is effectively governed by operation of the cable drive 60. The upper and lower belts 61, 62 of the cable drive 60 engage the central portion 16 of the cable 1 and, by operation of the drive motor 67, drive the central portion 1 b of the cable 1 through the bulb forming device 80. The longitudinal displacement of the central portion 1 b of the cable 1 along its path is measured, whilst the cable 1 is being driven, by way of the shaft encoder 71A, 71B. The output pulses generated by the shaft encoder 71A, 71B are converted into a measure of longitudinal displacement of the cable 1 utilising the known relationship between rotary displacement of the drive shaft 69/encoder wheel 72 and longitudinal displacement of the cable 1. When the central portion 1 b of the cable 1 has been displaced a predetermined distance as measured by the shaft encoder 71A, 71B, corresponding to the desired location for formation of a bulb in the cable 1 between the first and second clamps 81, 82 of the bulb forming device 80, the drive motor 67 is stopped. This stops the central portion 1 b of the cable 1. Referring to FIG. 4B, the first and second clamps 81, 82 of the bulb forming device 80 are then activated by way of the first and second hydraulic rams 85, 89 to clamp the central portion 1 b of the cable 1 between the first and second clamp upper and lower jaws 83, 84, 87, 88. Referring to FIG. 4C, the hydraulic ram 91 is then activated to displace the first clamp 81 toward the second clamp 82, thereby compressing the section of cable 1 located between the first and second clamps 81, 82. At the same time, for embodiments utilising the rotating cam mechanism 92, rotation of the first clamp 81 relative to the second clamp 82 partially unwinds (or opens) the wires of the section of cable 1 positioned between the first and second clamps 81, 82. The compression and opening of the cable buckles the wires of the cable so as to form a bulb 2 as depicted (during the early stage of its formation) in FIG. 4C.

To allow uninhibited advance of the first clamp 81 and section of cable 1 clamped by the first clamp 81 during the bulb forming operation, the cable drive 60 is allowed to freely idle during advancement of the first clamp 81. This idling may be achieved either by disengaging the primary gearbox 68 or secondary gearboxes 70, or by utilizing a form of drive motor having an internal brake mechanism that may be disengaged to allow the output shaft to freely spin when the drive motor is stopped. Whilst the cable drive 60 is allowed to idle and the first clamp 81 is displaced during the bulb forming sequence, the section of cable clamped by the first clamp 81 and the cable upstream of the first clamp 81 advances a distance equal to the displacement of the first clamp 81. The section of the cable 1 that is clamped by the second clamp 82, and the portion of the cable 1 downstream of the second clamp 82 remains stationary. Given that it is the length of the finished cable product, and spacing between bulbs in the finished product, that is sought to be controlled, the displacement of the upstream section of the cable during the bulb forming sequence is to be disregarded when measuring displacement of the cable 1. Accordingly, whilst the cable drive 60 is allowed to idle, output from the shaft encoder is disregarded for purposes of measuring displacement of the cable 1.

Once the bulb 2 has been formed in the cable 1 the hydraulic pressure in the hydraulic ram 91 is released. This releases the force acting on the first clamp, thereby releasing compressive force acting on the bulbed central portion 1 b of the cable. With release of the compressive force, the central portion 1 b of the cable elastically recovers slightly under a springback effect, reducing the diameter of the bulb 2 slightly and allowing the first clamp 81 to displace slightly away from the second clamp 82 under idle. The minor displacement of the upstream portion of the cable 1 during this momentary “relaxing” step is again disregarded for the purpose of measuring displacement of the cable 1. The first and second clamps 81, 82 are then released from the cable 1 and the first clamp 81 retracted to its original position by way of the hydraulic ram 91. The cable drive 60 then re-engages and is operated to further drive the cable 1 through the bulb forming device 80.

The further displacement of the cable 1 whilst it is being driven by the cable drive 60 is again measured by the shaft encoder 71A, 71B. Once the further displacement measured is equal to a further predetermined displacement, the drive motor 67 is again stopped so as to stop the central portion 1 b of the cable 1 in readiness for formation of a further bulb. In the preferred embodiment, displacement of the cable 1 is only measured for the purpose of determining when to stop the cable 1 whilst the cable 1 is being driven by the cable drive 60, with displacement during idling of the cable drive 60 being disregarded. It is also envisaged, however, that the displacement of the cable 1 might be measured throughout the full sequence, with the displacement of the cable 1 whilst the cable drive 60 is idling (which displacement is equal to the known displacement of the first clamp 81) being deducted from the total displacement for each cycle. This will result again in a displacement equal to the displacement measured during driving of the cable 1 by the cable drive 60.

Throughout the entire continuous process, the pay-out reel 20 and take-up reel 120 are rotatably driven by the respective drive motors 22, 122. The continuous rotation of the pay-out and take-up reels 20, 120 is made possible by decoupling the pay-out and take-up reels 20, 120 from the intermittent operation of the cable drive 60 and bulb forming device 80 by the upstream and downstream accumulators 40, 100. Whilst the cable drive 60 is advancing the cable 1, the increasing tension applied to the upstream portion 1 a of the cable 1 by the cable drive 60 increases the upward force acting on the upstream dancer roll 41, such that the upstream dancer roll 41 is displaced upwardly tending to reduce the tension in the upstream portion 1 a of the cable 1 back toward a constant value. The upward movement of the upstream dancer roll 41 also tends to straighten out the path of the upstream portion of the cable 1, thereby effectively decumulating the cable. The vertical position of the upstream dancer roll 41 is sensed by a photo-electric sensor, the output of which is processed by the control system which sends a proportional DC voltage output to the variable speed first cable drive motor 22, increasing the speed of the pay-out reel proportionally with the vertical position of the upstream dancer roll 41. This ensures that the upstream dancer roll 41 does not reach the uppermost limit of its range of travel and also tends to retain a relatively constant tension in the upstream portion 1 a of the cable 1. The control system further adjusts the speed of the drive motor 22 based on the torque load on the drive motor 22, which is directionally proportional to the tension in the upstream portion of the cable 1. With increased torque (resulting from increased cable tension) the speed of the first cable drive motor 22 will be increased so to increase the speed of the pay-out reel 20. This again tends to maintain constant tension in the cable 1. The response sensitivity of this control system may be manually adjusted by the operator by way of a potentiometer.

The moment the cable drive 60 first stops in preparation for operation of the cable forming device 80, as depicted in FIG. 2A, the upstream dancer roll 41 will typically be located toward the top of its range of travel. Once the cable drive 60 stops, such that the central portion 1 b of the cable 1 is no longer being advanced, no tension is applied to the upstream portion 1 a of the cable 1 by the cable drive 60, thereby reducing tension in the upstream portion 1 a of the cable 1. The first dancer roll 41, under action of gravity and the pneumatic pressure within the first piston 48, will be displaced downwardly, deflecting the path of the upstream portion 1 a of the cable 1 downwardly and tending to maintain the tension within the upstream portion 1 a of the cable 1. In response to the downward displacement of the first dancer roll 41 and a reduction in the tension in the upstream portion 1 a of the cable 1, the pay-out reel 20 will be controlled to slow down, again tending to maintain relatively constant tension within the upstream portion 1 a of the cable 1 and to prevent the upstream dancer roll 41 reaching the lowermost extent of its range of travel. At the completion of the bulb forming operation of the bulb forming device 80, and immediately prior to commencement of further advancement of cable 1 by the cable drive device 60, the upstream dancer roll 41 will typically be located toward the bottom of its range of travel, as depicted in FIG. 2B. It is envisaged that, in certain applications, the pay-out reel 20 may almost stop, or even momentarily stop, if the upstream dancer roll 41 comes close to the lowermost extent of its range of travel, prior to the end of the bulb forming operation.

Accordingly, throughout the continuous operation of the production line, the pay-out reel 20 is able to at least substantially continue being rotatably driven by the drive motor 22, which merely adjusts its speed to compensate for intermittent stopping and starting of the cable drive 60 without the need to expend significant energy in stopping and re-starting.

The downstream accumulator 100 and take-up reel 120 operate in a similar manner to the upstream accumulator 40 and pay-out reel 20, although the operation is effectively in reverse. Driving the cable 1 by the cable drive 60 tends to reduce the tension in the downstream portion 1 c of the cable 1. Accordingly, gravity and pressure within the cylinder 108 displace the downstream dancer roll 101 downwardly tending to increase the tension in the downstream portion 1 c of the cable 1, compensating for the decrease in tension resulting from the operation of the cable drive 60. Relatively constant tension is also tended to be maintained by increasing the speed of the take-up reel 120 as the downstream dancer roll 101 moves downwardly and when torque acting on the take-up reel 120 reduces, utilising a control system equivalent to that discussed above in relation to the pay-out reel 20. Immediately prior to operation of the bulb forming device 80, the downstream dancer roll 101 will typically be in a relatively low position, as generally depicted in FIG. 2A. Whilst the cable drive 60 is stopped, rotation of the take-up reel 120 will tend to increase the tension in the downstream portion of the cable 1, thereby driving the downstream dancer roll 101 upward, decumulating cable and tending to reduce the otherwise increasing tension in the downstream portion 1 a of the cable 1. The upward displacement of the downstream dancer roll 101 and increase in tension in the downstream portion 1 c of the cable 1 also results in control of the take-up reel 120 to reduce its speed. Again it is envisaged that, in certain applications, the take-up reel 120 may almost stop, or even momentarily stop if the downstream dancer roll 101 comes close to the uppermost extent of its range of travel during the bulb forming operation.

As the cable 1 is accumulated onto the take-up reel 120, the distribution wheel 125 is cyclically displaced laterally so as to evenly coil the cable onto the take-up reel 120. The cable 1 is continuously rolled onto the take-up reel 120 with bulbs 2 spaced along the cable 1. The continuous length of bulbed cable may then be unwound from the take-up reel 120 and cut into desired lengths to form individual cable bolts. This will typically be conducted on site in the mine. In scenarios where individual supplies of bulbed cable are desired that are less than the length of cable available from a single supply reel, the bulbed cable coiled onto the take-up reel 120 may be cut to the desired production length by way of the cutting device 98.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. For example, for production lines where it is desired to produce individual cut lengths of cable bolt rather than a coiled supply of multiple lengths of cable bolt for cutting to length on site, the downstream accumulator 100 and take-up reel 120 may be omitted. In such an embodiment of the apparatus, the cutting device 98 would cut off each length of cable bolt as it passes, with the cable bolt lengths collected in a tray or other collection means immediately downstream of the cutting device 98. It is also envisaged that the downstream accumulator 100 and take-up reel 120 might be laterally displaceable such that they can be displaced from an operable position within the production line downstream of the cutting device 98, for producing a coiled supply of cable bolts, to an inoperable position to the side of the production line to allow collection of individual lengths of cable bolt cut to length by the cutting device 98 in a tray moved into position downstream of the cutting device 98.

Embodiments are also envisaged where the pay-out reel and upstream accumulator are replaced with an alternate cable supply that might be advanced from the cable supply manually or by the cable drive 60, whilst retaining the downstream accumulator and take-up reel. 

1. An apparatus for manufacturing a cable bolt, said apparatus comprising: a rotatably driven pay-out reel for paying out a cable coiled in use about said pay-out reel; an upstream accumulator, located downstream of said pay-out reel, for accumulating cable advanced from said pay-out reel; a bulb forming device, located downstream of said upstream accumulator, for forming a bulb in cable advanced from said upstream accumulator; a cable drive, located downstream of said upstream accumulator, for advancing cable through said bulb forming device; wherein said pay-out reel is configured to rotate at least substantially continuously whilst said cable drive is configured to advance the cable after formation of each bulb to a position for formation of a subsequent bulb in the cable, said cable drive stopping a central portion of the cable downstream of said upstream accumulator for formation of the subsequent bulb, said upstream accumulator accumulating or decumulating an upstream portion of the cable as required throughout operation of said apparatus to allow at least substantially continual rotation of said pay-out reel whilst the central portion of the cable is stationary.
 2. The apparatus of claim 1, further comprising: a downstream accumulator, located downstream of said bulb forming device and said cable drive, for accumulating cable advanced from said bulb forming device; and a rotatably driven take-up reel for taking up cable advanced from said downstream accumulator; wherein said take-up reel is configured to rotate at least substantially continuously, said downstream accumulator accumulating or decumulating a downstream portion of the cable as required throughout operation of said apparatus to allow at least substantially continuous rotation of said take-up reel whilst the central portion of the cable is stationary.
 3. The apparatus of claim 1, wherein said cable drive is located upstream of said bulb forming device.
 4. The apparatus of claim 1, wherein said upstream accumulator is configured to engage an upstream portion of the cable and deflect the path of the upstream portion of the cable in a direction tending to maintain a constant tension in the upstream portion of the cable.
 5. The apparatus of claim 4, wherein said upstream accumulator comprises a pulley mounted on a displaceable shaft.
 6. The apparatus of claim 2, wherein said downstream accumulator is configured to engage a downstream portion of the cable and deflect the path of the upstream portion of the cable in a direction tending to maintain a constant tension in the upstream portion of the cable.
 7. The apparatus of claim 6, wherein said downstream accumulator comprises a pulley mounted on a displaceable shaft.
 8. The apparatus of claim 1, wherein said bulb forming device comprises: a first clamp adapted to releasably clamp the central portion of the cable with the central portion of the cable extending along a longitudinal axis; a second clamp longitudinally spaced from said first clamp and adapted to releasably clamp the central portion of the cable with the central portion of the cable extending along said longitudinal axis; and a clamp displacement drive for longitudinally displacing said first clamp, relative to said second clamp, along said longitudinal axis.
 9. The apparatus of claim 2 further comprising a cutting device, located downstream of said bulb forming device for cutting cable advanced from said bulb forming device, wherein said downstream accumulator and said take-up reel accumulator are displaceable from an operative position downstream of said bulb forming device.
 10. An apparatus for manufacturing a cable bolt, said apparatus comprising: a cable supply; a bulb forming device, located downstream of said cable supply, for forming a bulb in cable advanced from said cable supply; a cable drive, located downstream of said cable supply, for advancing cable through said bulb forming device; a downstream accumulator, located downstream of said bulb forming device and said cable drive, for accumulating cable advanced from said bulb forming device; and a rotatably driven take-up reel for taking up cable advanced from said downstream accumulator; wherein said said take-up reel is configured to rotate at least substantially continuously whilst said cable drive is configured to advance the cable after formation of each bulb to a position for formation of a subsequent bulb in the cable, said cable drive stopping a central portion of the cable between said cable supply and said downstream accumulator for formation of the successive bulb, said downstream accumulator accumulating or decumulating a downstream portion of the cable as required throughout operation of said apparatus to allow at least substantially continuous rotation of said take-up reel whilst the central portion of the cable is stationary.
 11. The apparatus of claim 1, wherein said cable drive is located upstream of said bulb forming device.
 12. The apparatus of claim 2, wherein said downstream accumulator is configured to engage a downstream portion of the cable and deflect the path of the upstream portion of the cable in a direction tending to maintain a constant tension in the upstream portion of the cable.
 13. The apparatus of claim 6, wherein said downstream accumulator comprises a pulley mounted on a displaceable shaft.
 14. The apparatus of claim 1, wherein said bulb forming device comprises: a first clamp adapted to releasably clamp the central portion of the cable with the central portion of the cable extending along a longitudinal axis; a second clamp longitudinally spaced from said first clamp and adapted to releasably clamp the central portion of the cable with the central portion of the cable extending along said longitudinal axis; and a clamp displacement drive for longitudinally displacing said first clamp, relative to said second clamp, along said longitudinal axis; further comprising a cutting device, located downstream of said bulb forming device, for cutting cable advanced from said bulb forming machine.
 15. A method for manufacturing a cable bolt, said method comprising: rotatably driving a pay-out reel having a cable coiled thereon to pay-out said cable from said pay-out reel; operating a cable drive, located downstream of said pay-out reel, to advance said cable through said cable drive and a bulb forming device; operating said cable drive to intermittently stop a central portion of said cable whilst continuing to rotatably drive said pay-out reel; whilst said central portion of said cable is stopped, forming a bulb in said central portion of said cable with said bulb forming device; and accumulating an upstream portion of said cable, located upstream of said cable drive and said bulb forming device, whilst said central portion of said cable is stopped.
 16. The method of claim 10, further comprising the steps of: rotatably driving a take-up reel, located downstream of said bulb forming device, to take up cable advanced from said bulb forming device; and accumulating a downstream portion of said cable, located downstream of said cable drive and said bulb forming device, whilst said portion of said cable is being advanced.
 17. A method for manufacturing a cable bolt, said method comprising: supplying cable from a cable supply; operating a cable drive, located downstream of said cable supply, to advance said cable through said cable drive and a bulb forming device; rotatably driving a take-up reel, located downstream of said bulb forming device, to take up cable advanced from said bulb forming device; operating said cable drive to intermittently stop a central portion of said cable whilst continuing to rotatably drive said take-up reel; whilst said central portion of said cable is stopped, forming a bulb in said central portion of said cable with said bulb forming device; and accumulating a downstream portion of said cable, located downstream of said cable drive and said bulb forming device, whilst said portion of said cable is being advanced.
 18. A method for manufacturing a cable bolt, said method comprising: a) driving a cable along a longitudinally extending path through a bulb forming device having an upstream clamp and a downstream clamp longitudinally spaced from said upstream clamp; b) at a position upstream of said bulb forming device, measuring displacement of said cable along said path whilst said cable is being driven; c) stopping at least a portion of said cable extending through said bulb forming device upon a first predetermined measured displacement of said cable equal to said displacement measured at step b); d) clamping said portion of said cable with said upstream clamp and said downstream clamp; e) displacing said upstream clamp towards said downstream clamp, thereby longitudinally compressing said portion of said cable to form a bulb in said portion of said cable; f) unclamping said portion of said cable; g) further driving said cable along said path; h) at said position upstream of said bulb forming device, measuring further displacement of said cable along said path whilst said cable is being further driven; i) stopping at least a further portion of said cable extending through said bulb forming device upon a further predetermined measured displacement of said cable equal to said further displacement measured at step h); j) clamping said further portion of said cable with said upstream clamp and said downstream clamp; k) displacing said upstream clamp towards said downstream clamp, thereby longitudinally compressing said further portion of said cable to form a further bulb in said further portion of said cable; l) unclamping said further portion of said cable; and m) repeating steps g) to l).
 19. The method of claim 18, wherein steps b) and f) are performed with a measuring device, output of said measuring device during step d) being disregarded when measuring displacement of said cable.
 20. The method of claim 19, wherein said measuring device is a rotary shaft encoder.
 21. The method of claim 20, wherein said shaft encoder is mounted on a wheel engaging said cable, said shaft encoder measuring rotation of said wheel.
 22. The method of claim 20, wherein said shaft encoder is coupled to a drive shaft of said cable drive, said shaft encoder measuring rotation of said drive shaft.
 23. The method of claim 18 wherein, immediately prior to unclamping said portion of said cable in step f), and immediately prior to unclamping said further portion of said cable in step l), a force applied to said upstream clamp to displace said upstream clamp toward said downstream clamp is removed, thereby allowing said upstream clamp to be displaced away from said downstream clamp during elastic recovery of said portion of said cable and during classic recovery of said further portion of said cable. 